Food-treatment apparatus with telescoping seal for air-circulating blower

ABSTRACT

A food-treatment apparatus, e.g. an oven, has a muffle defining a closed chamber in which food is heated and a fan in this chamber for circulating air therein during food treatment and pyroliztic self-cleaning thereafter. This fan is powered by a motor outside the muffle and extends through an opening in the muffle wall. A pair of nested telescoping angle-profile or flanged rings, one attached to the inside face of that wall and the other to its outside face carrying the motor are separated by an insulating ring, e.g. of asbestos, and surround the fan in the opening to form a thermally yielding seal and motor support.

United States Patent Eckhardt [54] F ODD-TREATMENT APPARATUS WITHTELESCOPING SEAL FOR AIR- CIRCULATING BLOWER [72] inventor:

[73] Assignee:

Werner Eckhardt, lm Gasschen, Germany Burger EisenwerkeAktiengesellschaft, Herborn, Dillkreis, Germany [22] Filed: Nov. 27,1970 [21] Appl.No.: 93,272

Maier ..'...126/21 A x Hurko et al.... ..l26/2l A PrimaryExaminer-Charles J. Myhre Attorney-Karl F. Ross ABSTRACT Afood-treatment apparatus, e.g. an oven, has a muffle defining a closedchamber in which food is heated and a fan in this chamber forcirculating air therein during food treatment and pyrolizticself-cleaning thereafter. This fan is powered by a motor outside themuffle and extends through an opening in the muffle wall. A pair ofnested telescoping angle-profile 0r flanged rings, one attached to theinside face of that wall and the other to its outside face carrying themotor are separated by an insulating ring, e.g. of asbestos, andsurround the fan in the opening to form a thermally yielding seal andmotor support.

9 Claims, 2 Drawing Figures Ill FOOD-TREATMENT APPARATUS WITHTELESCOPING SEAL FOR AIR-CIRCULATING BLOWER l. CROSS-REFERENCE TOCOPENDING APPLICATIONS.

This application discloses an improvement in the systems described andclaimed in the commonly assigned copending applications, serial numbers778,123, now US Pat. No. 3,550,576, and 778,269 filed Nov. 22, 1968 andSer. Nos. 40,127 and 40,128 filed May 25,1970.

2. FIELD OF THE INVENTION The present invention relates r afood-treatment apparatus. More specifically this invention concerns anoven used for the thermal treatment, 'e.g. baking, broiling, orcomestibles and provided with so-called self-cleaning means.

3. BACKGROUND OF THE INVENTION Such a self-cleaning apparatus is oftenprovided with a fan inside its treatment chamber which is operated tocirculate gases therein during cooking or cleaning for even heatdistribution. During self-cleaning, when temperatures of about 500 C.are necessary for the pyrolitic decomposition and/or combustion of foodresidue, it is necessary to protect the fan motor. This has been done inthe past through the simple expedient of. mounting the motor outside thetreatment chamber, with the fan extending through a wall of the chamberas described in the above-mentioned applications for example.

Such methods have not proven wholly effective, especially during theself-cleaning operation. Enough heat often passes through the openingthrough which the blower extends to damage the motor, even thoughelaborate methods of sealing this opening have been used.

It has been found that an important reason for heat leaks at this pointis the expansion of the muffle walls during heating. A seal which isexcellent when the apparatus is at room temperature opens when it isheated. At the same time, the various structure constituting the sealarrangement often serve to conduct heat out ofthe chamber and to themotor.

4. OBJECTS OF THE INVENTION It is, therefore, an object of the presentinvention to provide an improved food-treatment apparatus of the generalcharacter described.

Another object is to provide a seal having particular adaptability to afood-treatment apparatus of the type described and claim ed in theabove-mentioned applications.

5. SUMMARY OF THE INVENTION The above objects are obtained according tothe present invention by an apparatus having a housing defining aclosable heatable chamber with one wall formed with an opening throughwhich blower means or circulating air in the chamber passes. Mountingmeans is provided which includes a first axially directed ring fixed toan inside face of the wall and extending outwardly in the opening and asecond axially directed ring telescopically received in the first ringand fixed to an outside face ofthe wall. The second ring extendsinwardly in the opening and the blower means extends through the ringsso that, when the wall expands on heating, they move axially relative toeach other. An important feature of the invention provides that themotor and fan assembly is mounted solely upon the annular outwardlyextending flange of the outer flanged ring and that this mounting meansis formed with a housing sleeve which is telescopingly received within,but is spaced circumferentially from the inner ring.

According to another feature of the present invention an annularcompressible seal ofinsulating material, e.g. asbestos, is providedbetween the two rings, and the ring attached to the inner face is nestedwithin the other ring. In this manner a tight seal is maintained bothduring axial shifting and during the inevitable radial expansion oftheinner ring.

In accordance with yet another feature of this invention on the motorfor the fan of the blower means is secured to an annular flange which isbolted to the flange of the outer ring, with interposition of athermally insulating washer. The sleeve and outer ring form a channelcoaxially receiving the rearwardly extending end of the inner ring andforming a labyrinth therewith, the labyrinth compartment between theinner and outer rings being filled with the asbestos layer. Anotherasbestos ring held between the parts of the fan assembly, hugs the innerwall of the inner ring ahead ofthe housing sleeve.

The housing defining the chamber is, according to yet another feature,formed by a thick body of insulating material such as Fiberglassandwiched between two metal sheets. The rings are angle rings eachattached to one of the sheets. In such a structure the expansion of theinner sheet relative to the outer sheet during heating is extreme sothat the seal of the present invention finds particular application.

6. DESCRIPTION OF THE DRAWING I The above and other objects, features,and advantages will become apparent from the following description,reference being made to the accompanying drawing, in which:

FIG. 1 is a vertical longitudinal section through an apparatus accordingto the present invention; and

FIG. 2 is a detail of FIG. 1 in enlarged scale.

7. SPECIFIC DESCRIPTION As shown in FIG. 1 an oven has a housing 10 ofsheet metal in which is provided a muffle 1 having a cooking chamber 4in which food to be cooked can be held on racks 11. The muffle 1 has oneend closed by a door 12 and another end 2 formed with an opening 13. Acatalytic afterburner 14 is provided in its top wall opening into aspace 15 between the housing 10 and the muffle l. A hood 16 is providedat the back of the cooking chamber 4 with its wide mouth open towardsthe door and its narrow mouth opening toward a fan 3 which extendsthrough the opening I3 and is connected to an electric drive motor 17received in a chamber 18 in back of the muffle 1 in the housing 10.

The muffle l is formed with thick walls comprising an metallic innerskin la and an metallic outer skin lb sandwiching a body of 1c ofinsulating material such as Fiberglas. Such a construction is extremelydurable and offers excellent thermal insulating properties so that, onheating of the chamber 4 by the electric element 19 disposed around thehood 16, very little heat is lost. It is possible to heat the chamber 4up to a around 450 centigrade for self-cleaning of the wall 1a and theracks 11, the noxious vapors being rendered harmless by the catalyticafterburner 14.

The fan 3 is adapted to be operated both during cooking andself-cleaning. To this end it comprises three coaxial portions, a pairof oppositely directed axial-input radial-output fans 3a and 3cseparated by a hub 3b. The fan 3a is received in the chamber 4 and, onrotation, pulls gases in axially through the hood l6 and expells themradially outwardly around this hood, as shown by the arrows 20. The fan30 is in the chamber I8 and serves to circulate air through the motor 17and expel it outwardly in this chamber as shown by the arrows 21, whenceit passes through the space 15 and out of the housing 10. The hub 3baxially spaces the two fans 30 and 3c and passes through the opening 13in the rear wall 2 of the muffle l. A discussion of how such a fanarrangement functions is to be found in the commonly assigned patentapplications mentioned above.

Bolted to the inner face of wall 2, with interposition of an insulatingwasher 22, is a ring 5 of L cross section. This angle ring 5 has, thus,an annular portion 5a bolted to and lying in a plane parallel to theinner wall 7 of the muffle end 2, and portion 5b of cylindrical shapeextending from the inner periphery of the attached portion 5a outwardlyin the opening 13. A similar L-section metallic ring 6 is provided withits flange portion 6a bolted directly to the outer face of the wall 2and and its cylindrical, axially directed portion 6b extending in theopening 13 inwardly toward the muffle 4. The ring portion 6b liescoaxial with and outside of the portion 511, with a cylindrical ring 8of asbestos insulating material compressed between these two portions.

An annular metallic body or sleeve 9 comprising a pair of substantiallyplanar and parallel portions separated by a cylindrical portion isbolted with the motor flange 24, an insulating gasket and the ringportion 6b to the wall 2. This body 9 also prevents heat loss throughthe opening 13 by controlling air currents therethrough and serves tocenter the fan 3 while defining with the rings a labyrinth seal. A gland23, advantageously of asbestos, engages at its outer periphery the ringportion 5b and has its thickened inner edge in engagement with the diskface of the back of the fan 3a.

On heating of the chamber 4 the inner metallic skin 1a of the muffle 1will expand, compressing slightly the insulating material 1c. At thesame time the rings 5 and 6 will move axially toward each other, and anyradially outward expansion ofthe ring portion 5b will be taken up by thecompressible ring 8. Thus, an effective seal is maintained at theopening 13in spite of the inevitable expansion, and subsequentcontraction, of the muffle 1, while permitting the fans and SC torotate. Even since the rings 5 and 6 and the fan 3 are all coaxial aboutan axis A orthogonal to the wall 2, the expansion of this wall will notcreate any difficulties. Even the extreme heat necessary for selfcleaning operations present no difficulties with a food-treatmentapparatus of this type.

1 claim:

1. An apparatus for the heat treatment ofa comestible comprising:

a housing defining a closable heatable chamber adapted to receive saidcomestible, said housing having a wall formed with an opening;

blower means extending through said opening for circulating air in saidchamber; and

mounting means including a first ring fixed to an inside face of saidwall and extending axially outwardly in said opening and a second ringtelescopically received in said first ring and fixed to an outside faceof said wall, said second ring extending axially inwardly in saidopening, said blower means extending through said rings, whereby onthermal expansion of said wall said rings move axially relative to eachother.

2. The apparatus defined in claim 1 wherein each of said rings is anangle ring with an annular flange portion attached to the respectiveface of said wall and a cylindrical portion extending from the innerperiphery of the flange portion.

3. The apparatus defined in claim 2 wherein said blower means includes afan rotatable about an axis, said cylindrical portions being coaxialwith said axis.

4. The apparatus defined in claim 3 wherein said wall is substantiallyflat and perpendicular to said axis.

5. The apparatus defined in claim 2, further comprising a ring ofcompressible insulating material between said cylindrical portions.

6. The apparatus defined in claim 1 wherein said wall includes an outermetallic skin forming said outer face, an inner metallic skin formingsaid inner face, and a body of compressible insulating material betweensaid skins.

7. The apparatus defined in claim 2 wherein said second ring attached tosaid outer face at least partially surrounds said first ring.

8. The apparatus defined in claim 1, further comprising an annularcentering body attached to said second ring, said blower means beingcentered in said body.

9. The apparatus defined in claim 8 wherein said body is a sleeveforming a labyrinth seal with said rings.

1. An apparatus for the heat treatment of a comestible comprising: ahousing defining a closable heatable chamber adapted to receive saidcomestible, said housing having a wall formed with an opening; blowermeans extending through said opening for circulating air in saidchamber; and mounting means including a first ring fixed to an insideface of said wall and extending axially outwardly in said opening and asecond ring telescopically received in said first ring and fixed to anoutside face of said wall, said second ring extending axially inwardlyin said opening, said blower means extending through said rings, wherebyon thermal expansion of said wall said rings move axially relative toeach other.
 2. The apparatus defined in claim 1 wherein each of saidrings is an angle ring with an annular flange portion attached to therespective face of said wall and a cylindrical portion extending fromthe inner periphery of the flange portion.
 3. The apparatus defined inclaim 2 wherein said blower means includes a fan rotatable about anaxis, said cylindrical portions being coaxial with said axis.
 4. Theapparatus defined in claim 3 wherein said wall is substantially flat andperpenDicular to said axis.
 5. The apparatus defined in claim 2, furthercomprising a ring of compressible insulating material between saidcylindrical portions.
 6. The apparatus defined in claim 1 wherein saidwall includes an outer metallic skin forming said outer face, an innermetallic skin forming said inner face, and a body of compressibleinsulating material between said skins.
 7. The apparatus defined inclaim 2 wherein said second ring attached to said outer face at leastpartially surrounds said first ring.
 8. The apparatus defined in claim1, further comprising an annular centering body attached to said secondring, said blower means being centered in said body.
 9. The apparatusdefined in claim 8 wherein said body is a sleeve forming a labyrinthseal with said rings.